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Davies A, Tomas A. Appreciating the potential for GPCR crosstalk with ion channels. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2023; 195:101-120. [PMID: 36707150 DOI: 10.1016/bs.pmbts.2022.06.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
G protein-coupled receptors (GPCRs) are expressed by most tissues in the body and are exploited pharmacologically in a variety of pathological conditions including diabetes, cardiovascular disease, neurological diseases, and cancers. Numerous cell signaling pathways can be regulated by GPCR activation, depending on the specific GPCR, ligand and cell type. Ion channels are among the many effector proteins downstream of these signaling pathways. Saliently, ion channels are also recognized as druggable targets, and there is evidence that their activity may regulate GPCR function via membrane potential and cytoplasmic ion concentration. Overall, there appears to be a large potential for crosstalk between ion channels and GPCRs. This might have implications not only for targeting GPCRs for drug development, but also opens the possibility of co-targeting them with ion channels to achieve improved therapeutic outcomes. In this review, we highlight the large variety of possible GPCR-ion channel crosstalk modes.
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Affiliation(s)
- Amy Davies
- Section of Cell Biology and Functional Genomics, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, United Kingdom
| | - Alejandra Tomas
- Section of Cell Biology and Functional Genomics, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, United Kingdom.
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2
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Chen W, Huang W, Pather SR, Chang W, Sung L, Wu H, Liao M, Lee C, Wu H, Wu C, Liao K, Lin C, Yang S, Lin H, Lai P, Ng C, Hu C, Chen I, Chuang C, Lai C, Lin P, Lee Y, Schuyler SC, Schambach A, Lu FL, Lu J. Podocalyxin-Like Protein 1 Regulates Pluripotency through the Cholesterol Biosynthesis Pathway. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 10:e2205451. [PMID: 36373710 PMCID: PMC9811443 DOI: 10.1002/advs.202205451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Indexed: 06/16/2023]
Abstract
Deciphering signaling mechanisms critical for the extended pluripotent stem cell (EPSC) state and primed pluripotency is necessary for understanding embryonic development. Here, a membrane protein, podocalyxin-like protein 1 (PODXL) as being essential for extended and primed pluripotency, is identified. Alteration of PODXL expression levels affects self-renewal, protein expression of c-MYC and telomerase, and induced pluripotent stem cell (iPSC) and EPSC colony formation. PODXL is the first membrane protein reported to regulate de novo cholesterol biosynthesis, and human pluripotent stem cells (hPSCs) are more sensitive to cholesterol depletion than fibroblasts. The addition of exogenous cholesterol fully restores PODXL knockdown-mediated loss of pluripotency. PODXL affects lipid raft dynamics via the regulation of cholesterol. PODXL recruits the RAC1/CDC42/actin network to regulate SREBP1 and SREBP2 maturation and lipid raft dynamics. Single-cell RNA sequencing reveals PODXL overexpression enhanced chimerism between human cells in mouse host embryos (hEPSCs 57%). Interestingly, in the human-mouse chimeras, laminin and collagen signaling-related pathways are dominant in PODXL overexpressing cells. It is concluded that cholesterol regulation via PODXL signaling is critical for ESC/EPSC.
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Affiliation(s)
- Wei‐Ju Chen
- Genomics Research CenterAcademia SinicaGenome and Systems Biology Degree ProgramCollege of Life ScienceNational Taiwan UniversityTaipei10617Taiwan
- Genomics Research CenterAcademia SinicaTaipei11529Taiwan
| | - Wei‐Kai Huang
- Center for Genomic MedicineMassachusetts General HospitalBostonMA02114USA
| | - Sarshan R. Pather
- Cell and Molecular Biology Graduate GroupPerelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPA19104USA
| | - Wei‐Fang Chang
- Institute of BiotechnologyNational Taiwan UniversityTaipei10617Taiwan
| | - Li‐Ying Sung
- Institute of BiotechnologyNational Taiwan UniversityTaipei10617Taiwan
- Agricultural Biotechnology Research CenterAcademia SinicaTaipei11529Taiwan
- Animal Resource CenterNational Taiwan UniversityTaipei10617Taiwan
| | - Han‐Chung Wu
- Institute of Cellular and Organismic BiologyAcademia SinicaTaipei11529Taiwan
- Biomedical Translation Research Center (BioTReC)Academia SinicaTaipei11529Taiwan
| | - Mei‐Ying Liao
- Institute of Cellular and Organismic BiologyAcademia SinicaTaipei11529Taiwan
| | - Chi‐Chiu Lee
- Institute of Cellular and Organismic BiologyAcademia SinicaTaipei11529Taiwan
| | - Hsuan‐Hui Wu
- Institute of Cellular and Organismic BiologyAcademia SinicaTaipei11529Taiwan
| | - Chung‐Yi Wu
- Genomics Research CenterAcademia SinicaTaipei11529Taiwan
| | | | - Chun‐Yu Lin
- Genomics Research CenterAcademia SinicaTaipei11529Taiwan
| | | | - Hsuan Lin
- Genomics Research CenterAcademia SinicaTaipei11529Taiwan
| | - Pei‐Lun Lai
- Genomics Research CenterAcademia SinicaTaipei11529Taiwan
| | - Chi‐Hou Ng
- Genomics Research CenterAcademia SinicaTaipei11529Taiwan
| | - Chun‐Mei Hu
- Genomics Research CenterAcademia SinicaTaipei11529Taiwan
| | - I‐Chih Chen
- Genomics Research CenterAcademia SinicaTaipei11529Taiwan
| | | | - Chien‐Ying Lai
- Genomics Research CenterAcademia SinicaTaipei11529Taiwan
| | - Po‐Yu Lin
- Genomics Research CenterAcademia SinicaTaipei11529Taiwan
| | - Yueh‐Chang Lee
- Department of OphthalmologyHualien Tzu Chi HospitalBuddhist Tzu Chi Medical FoundationHualien97004Taiwan
| | - Scott C. Schuyler
- Department of Biomedical SciencesCollege of MedicineChang Gung UniversityDivision of Head and Neck SurgeryDepartment of OtolaryngologyChang Gung Memorial HospitalTaoyuan33302Taiwan
| | - Axel Schambach
- Institute of Experimental HematologyHannover Medical School30625HannoverGermany
| | - Frank Leigh Lu
- Department of PediatricsNational Taiwan University Hospital and National Taiwan University Medical CollegeTaipei10051Taiwan
| | - Jean Lu
- Genomics Research CenterAcademia SinicaGenome and Systems Biology Degree ProgramCollege of Life ScienceNational Taiwan UniversityTaipei10617Taiwan
- Genomics Research CenterAcademia SinicaTaipei11529Taiwan
- National RNAi Platform/ National Core Facility Program for BiotechnologyTaipei11529Taiwan
- Department of Life ScienceTzu Chi UniversityHualien97004Taiwan
- Graduate Institute of Medical SciencesNational Defense Medical CenterTaipei11490Taiwan
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3
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Ton Tran HT, Li C, Chakraberty R, Cairo CW. NEU1 and NEU3 enzymes alter CD22 organization on B cells. BIOPHYSICAL REPORTS 2022; 2:100064. [PMID: 36425332 PMCID: PMC9680808 DOI: 10.1016/j.bpr.2022.100064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 07/19/2022] [Indexed: 06/16/2023]
Abstract
The B cell membrane expresses sialic-acid-binding immunoglobulin-like lectins, also called Siglecs, that are important for modulating immune response. Siglecs have interactions with sialoglycoproteins found on the same membrane (cis-ligands) that result in homotypic and heterotypic receptor clusters. The regulation and organization of these clusters, and their effect on cell activation, is not clearly understood. We investigated the role of human neuraminidase enzymes NEU1 and NEU3 on the clustering of CD22 on B cells using confocal microscopy. We observed that native NEU1 and NEU3 activity influence the cluster size of CD22. Using single-particle tracking, we observed that NEU3 activity increased the lateral mobility of CD22, which was in contrast to the effect of exogenous bacterial NEU enzymes. Moreover, we show that native NEU1 and NEU3 activity influenced cellular Ca2+ levels, supporting a role for these enzymes in regulating B cell activation. Our results establish a role for native NEU activity in modulating CD22 organization and function on B cells.
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Affiliation(s)
- Hanh-Thuc Ton Tran
- Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Caishun Li
- Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
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4
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Xu X, Wang Y, Choi WS, Sun X, Godbout R. Super resolution microscopy reveals DHA-dependent alterations in glioblastoma membrane remodelling and cell migration. NANOSCALE 2021; 13:9706-9722. [PMID: 34018532 DOI: 10.1039/d1nr02128a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Brain fatty acid binding protein (FABP7; B-FABP) promotes glioblastoma (GBM) cell migration and is associated with tumor infiltration, properties associated with a poor prognosis in GBM patients. FABP7-expressing neural stem-like cells are known to drive tumor migration/infiltration and resistance to treatment. We have previously shown that FABP7's effects on cell migration can be reversed when GBM cells are cultured in medium supplemented with the omega-3 fatty acid, docosahexaenoic acid (DHA). Here, we use super-resolution imaging on patient-derived GBM stem-like cells to examine the importance of FABP7 and its fatty acid ligands in mitigating GBM cell migration. As FABPs are involved in fatty acid transport from membrane to cytosol, we focus on the effect of FABP7 and its ligand DHA on GBM membrane remodeling, as well as FABP7 nanoscale domain formation on GBM membrane. Using quantitative plasma membrane lipid order imaging, we show that FABP7 expression in GBM cells correlates with increased membrane lipid order, with DHA dramatically decreasing lipid order. Using super-resolution stimulated emission depletion (STED) microscopy, we observe non-uniform distribution of FABP7 on the surface of GBM cells, with FABP7 forming punctate nanoscale domains of ∼100 nm in diameter. These nanodomains are particularly enriched at the migrating front of GBM cells. Interestingly, FABP7 nanodomains are disrupted when GBM cells are cultured in DHA-supplemented medium. We demonstrate a tight link between cell migration, a higher membrane lipid order and increased FABP7 nanoscale domains. We propose that DHA-mediated disruption of membrane lipid order and FABP7 nanodomains forms the basis of FABP7/DHA-mediated inhibition of cell migration in GBM.
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Affiliation(s)
- Xia Xu
- Cross Cancer Institute, University of Alberta, Department of Oncology, 11560 University Avenue, Edmonton, Alberta, Canada.
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5
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Bag N, Holowka DA, Baird BA. Imaging FCS delineates subtle heterogeneity in plasma membranes of resting mast cells. Mol Biol Cell 2020; 31:709-723. [PMID: 31895009 PMCID: PMC7202073 DOI: 10.1091/mbc.e19-10-0559] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
A myriad of transient, nanoscopic lipid- and protein-based interactions confer a steady-state organization of the plasma membrane in resting cells that is poised to orchestrate assembly of key signaling components upon reception of an extracellular stimulus. Although difficult to observe directly in live cells, these subtle interactions can be discerned by their impact on the diffusion of membrane constituents. Here, we quantified the diffusion properties of a panel of structurally distinct lipid, lipid-anchored, and transmembrane (TM) probes in RBL mast cells by imaging fluorescence correlation spectroscopy (ImFCS). We developed a statistical analysis of data combined from many pixels over multiple cells to characterize differences in diffusion coefficients as small as 10%, which reflect differences in underlying interactions. We found that the distinctive diffusion properties of lipid probes can be explained by their dynamic partitioning into Lo-like proteolipid nanodomains, which encompass a major fraction of the membrane and whose physical properties are influenced by actin polymerization. Effects on diffusion of functional protein modules in both lipid-anchored and TM probes reflect additional complexity in steady state membrane organization. The contrast we observe between different probes diffusing through the same membrane milieu represents the dynamic resting steady state, which serves as a baseline for monitoring plasma membrane remodeling that occurs upon stimulation.
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Affiliation(s)
- Nirmalya Bag
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853
| | - David A Holowka
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853
| | - Barbara A Baird
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853
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6
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Wu Y, Zhao Y, He X, He Z, Wang T, Wan L, Chen L, Yan N. Hydroxypropyl‑β‑cyclodextrin attenuates the epithelial‑to‑mesenchymal transition via endoplasmic reticulum stress in MDA‑MB‑231 breast cancer cells. Mol Med Rep 2019; 21:249-257. [PMID: 31746388 PMCID: PMC6896369 DOI: 10.3892/mmr.2019.10802] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 10/02/2019] [Indexed: 01/04/2023] Open
Abstract
The epithelial-to-mesenchymal transition (EMT) has been reported to serve vital roles in regulating the progress of cancer metastasis. In addition, lipid rafts enriched in sphingolipids and cholesterol serve important roles in physiological and biochemical processes as a signaling platform. The present study explored the effects of hydroxypropyl-β-cyclodextrin (HP-β-CD), a cholesterol-depleting agent of lipid rafts, on the transforming growth factor (TGF)-β/Smad signaling pathway and endoplasmic reticulum (ER) stress in mediating EMT in MDA-MB-231 breast cancer cells. HP-β-CD treatment inhibited TGF-β1-induced EMT, based on increased expression of E-cadherin and decreased expression of vimentin. HP-β-CD reduced the expression of the TGF receptor TβRI and blocked the phosphorylation of Smad2. In addition, HP-β-CD increased the expression of ER stress-related proteins (binding immunoglobulin protein and activating transcription factor 6), but TGF-β1 could reverse these changes. Sodium 4-phenylbutyrate, an inhibitor of ER stress, suppressed these effects of HP-β-CD on EMT and TGF-β/Smad signaling pathway inhibition in breast cancer cells. Thus, HP-β-CD can block the TGF-β/Smad signaling pathway via diminishing the expression of TβRI which helps to activate ER stress and attenuate EMT in MDA-MB-231 cells, highlighting a potential target of lipid rafts for breast cancer treatment.
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Affiliation(s)
- Yifan Wu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Nanchang University, Nanchang, Jiangxi 330006, P.R. China
| | - Yiyang Zhao
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Nanchang University, Nanchang, Jiangxi 330006, P.R. China
| | - Xuanhong He
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Nanchang University, Nanchang, Jiangxi 330006, P.R. China
| | - Zhiqiang He
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Nanchang University, Nanchang, Jiangxi 330006, P.R. China
| | - Tian Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Nanchang University, Nanchang, Jiangxi 330006, P.R. China
| | - Linxi Wan
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Nanchang University, Nanchang, Jiangxi 330006, P.R. China
| | - Lai Chen
- Laboratory Animal Research Center for Science and Technology, Jiangxi University of Traditional Chinese Medicine, Nanchang, Jiangxi 330004, P.R. China
| | - Nianlong Yan
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Nanchang University, Nanchang, Jiangxi 330006, P.R. China
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7
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Iyer SS, Tripathy M, Srivastava A. Fluid Phase Coexistence in Biological Membrane: Insights from Local Nonaffine Deformation of Lipids. Biophys J 2019; 115:117-128. [PMID: 29972803 DOI: 10.1016/j.bpj.2018.05.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 05/10/2018] [Accepted: 05/15/2018] [Indexed: 01/09/2023] Open
Abstract
Lateral heterogeneities in biomembranes play a crucial role in various physiological functions of the cell. Such heterogeneities lead to demixing of lipid constituents and formation of distinct liquid domains in the membrane. We study lateral heterogeneities in terms of topological rearrangements of lipids to identify the liquid-liquid phase coexistence in model membranes. Using ideas from the physics of amorphous systems and glasses, we calculate the degree of nonaffine deformation associated with individual lipids to characterize the liquid-ordered (Lo) and liquid-disordered (Ld) regions in model lipid bilayers. We explore the usage of this method on all-atom and coarse-grained lipid bilayer trajectories. This method is helpful in defining the instantaneous Lo-Ld domain boundaries in complex multicomponent bilayer systems. The characterization is also used to highlight the effect of line-active molecules on the phase boundaries and domain mixing. Overall, we propose a framework to explore the molecular origin of spatial and dynamical heterogeneity in biomembrane systems, which can be exploited not only in computer simulations but also in experiments.
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Affiliation(s)
- Sahithya S Iyer
- Molecular Biophysics Unit, Indian Institute of Science Bangalore, Bangalore, Karnataka, India
| | - Madhusmita Tripathy
- Molecular Biophysics Unit, Indian Institute of Science Bangalore, Bangalore, Karnataka, India
| | - Anand Srivastava
- Molecular Biophysics Unit, Indian Institute of Science Bangalore, Bangalore, Karnataka, India.
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8
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Proteomic Analysis of Lipid Rafts from RBL-2H3 Mast Cells. Int J Mol Sci 2019; 20:ijms20163904. [PMID: 31405203 PMCID: PMC6720779 DOI: 10.3390/ijms20163904] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 08/01/2019] [Accepted: 08/08/2019] [Indexed: 12/15/2022] Open
Abstract
Lipid rafts are highly ordered membrane microdomains enriched in cholesterol, glycosphingolipids, and certain proteins. They are involved in the regulation of cellular processes in diverse cell types, including mast cells (MCs). The MC lipid raft protein composition was assessed using qualitative mass spectrometric characterization of the proteome from detergent-resistant membrane fractions from RBL-2H3 MCs. Using two different post-isolation treatment methods, a total of 949 lipid raft associated proteins were identified. The majority of these MC lipid raft proteins had already been described in the RaftProtV2 database and are among highest cited/experimentally validated lipid raft proteins. Additionally, more than half of the identified proteins had lipid modifications and/or transmembrane domains. Classification of identified proteins into functional categories showed that the proteins were associated with cellular membrane compartments, and with some biological and molecular functions, such as regulation, localization, binding, catalytic activity, and response to stimulus. Furthermore, functional enrichment analysis demonstrated an intimate involvement of identified proteins with various aspects of MC biological processes, especially those related to regulated secretion, organization/stabilization of macromolecules complexes, and signal transduction. This study represents the first comprehensive proteomic profile of MC lipid rafts and provides additional information to elucidate immunoregulatory functions coordinated by raft proteins in MCs.
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Knežević M, Jiang H, Wang S. Active Tuning of Synaptic Patterns Enhances Immune Discrimination. PHYSICAL REVIEW LETTERS 2018; 121:238101. [PMID: 30576186 DOI: 10.1103/physrevlett.121.238101] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 07/07/2018] [Indexed: 06/09/2023]
Abstract
Immune cells learn about their antigenic targets using tactile sense: a self-organized motif named immunological synapse forms between an immune cell and an antigen-presenting cell (APC) during recognition. Via synapses, immune cells apply mechanical pulling forces to selectively extract antigen (Ag) from APCs. Curiously, depending on its stage of development, a B lymphocyte exhibits distinct synaptic patterns and uses force at different strength and timing, which appears to strongly impact its ability to distinguish Ag affinities. We use a statistical-mechanical model to study how the experimentally observed synaptic architectures can originate from normal cytoskeletal forces coupled to the lateral organization of mobile receptors, and show how this active regulation scheme, collective in nature, may enhance the efficiency and capacity of discrimination.
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Affiliation(s)
- Miloš Knežević
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
| | - Hongda Jiang
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
| | - Shenshen Wang
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
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10
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Ray A, Gräter F, Thukral L. Probing molecular forces in multi-component physiological membranes. Phys Chem Chem Phys 2018; 20:2155-2161. [PMID: 29177331 DOI: 10.1039/c7cp05981g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Biological membranes are remarkably heterogeneous, composed of diverse lipid mixtures with distinct chemical structure and composition. By combining molecular dynamics simulations and the newly developed Lipid-Force Distribution Analysis (L-FDA), we explore force transmission in complex multi-component membrane models mimicking eukaryotic organelles. We found that the chemical-moiety based segmentation at membrane interfaces revealed a distinctive distribution of bonded and non-bonded forces in diverse membrane environment. Our molecular stress analysis could have far-reaching implications in describing the relationship between membrane mechanical properties and functional states of chemically distinct lipids.
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Affiliation(s)
- Arjun Ray
- CSIR-Institute of Genomics and Integrative Biology, Mathura Road, New Delhi, 110025, India.
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11
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Badana AK, Chintala M, Gavara MM, Naik S, Kumari S, Kappala VR, Iska BR, Malla RR. Lipid rafts disruption induces apoptosis by attenuating expression of LRP6 and survivin in triple negative breast cancer. Biomed Pharmacother 2017; 97:359-368. [PMID: 29091885 DOI: 10.1016/j.biopha.2017.10.045] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Revised: 10/08/2017] [Accepted: 10/09/2017] [Indexed: 01/18/2023] Open
Abstract
Triple negative breast cancer is a clinically challenging subtype due to lack of biomarker for rational targeted therapy. Lipid rafts are cholesterol enriched rigid platforms, which colocalize signalling molecules of cancer progression. This study explores the effect of lipid rafts disruption by cholesterol depleting agent, MβCD on induction of apoptosis and expression of WNT receptor LRP6, survivin and common apoptotic markers in TNBC cell lines. The in vitro effect of lipid rafts disruption on viability, single cell reproductive ability, proliferation and migration were evaluated by MTT, clonogenic, BrdU incorporation and wound scratch assays, respectively. The morphological changes were assessed by tryphan blue, Wright and Giemsa staining; nuclear changes by Hoechst staining. The induction of apoptosis was evaluated by AO/EtBr staining, DNA damage and DNA fragmentation assays. Expression of Caveolin-1, LRP6, β-Catenin, Survivin, Bcl2, BAX, Caspase-3, Ki67 and c-myc were analyzed by PCR and Western blotting techniques. The lipid raft disruption resulted in reduction of the proliferation of MDA-MB 231 and MDA-MB 468 cells by 56.3 and 42.0%; survival fraction by 54.7 and 59.4%; migration by 44.3 and 48.4%, respectively. It also induced apoptosis by causing cell shrinkage, membrane blebbing, nuclear condensation, chromatin cleavage, oligonucleotide fragmentation with an apoptotic index of 59.1 and 46.6% in MDA-MB 231 and 468 cells, respectively. Further, it downregulated the expression of caveolin-1, LRP6, β-catenin, survivin, Bcl2, ki67, c-myc and upregulated BAX, caspase-3. The cholesterol supplementation enhanced the clonogenic potential and upregulated the expression of caveolin-1 and LRP6. The results underline a potential effect of lipid rafts disruption on induction of apoptosis in TNBC cells.
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Affiliation(s)
- Anil Kumar Badana
- Cancer Biology Research Laboratory, Department of Biochemistry, GIS, GITAM University, Visakhapatnam, India
| | - Madhuri Chintala
- Department of Obstetrics & Gynecology, Andhra Medical College, Visakhapatnam, India
| | - Murali Mohan Gavara
- Cancer Biology Research Laboratory, Department of Biochemistry, GIS, GITAM University, Visakhapatnam, India
| | - Shailender Naik
- Cancer Biology Research Laboratory, Department of Biochemistry, GIS, GITAM University, Visakhapatnam, India
| | - Seema Kumari
- Cancer Biology Research Laboratory, Department of Biochemistry, GIS, GITAM University, Visakhapatnam, India
| | | | | | - Rama Rao Malla
- Cancer Biology Research Laboratory, Department of Biochemistry, GIS, GITAM University, Visakhapatnam, India; Department of Biochemistry, GIS, GITAM University, Visakhapatnam, India.
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12
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Dharan N, Farago O. Interplay between membrane elasticity and active cytoskeleton forces regulates the aggregation dynamics of the immunological synapse. SOFT MATTER 2017; 13:6938-6946. [PMID: 28825081 DOI: 10.1039/c7sm01064h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Adhesion between a T cell and an antigen presenting cell is achieved by TCR-pMHC and LFA1-ICAM1 protein complexes. These segregate to form a special pattern, known as the immunological synapse (IS), consisting of a central quasi-circular domain of TCR-pMHC bonds surrounded by a peripheral domain of LFA1-ICAM1 complexes. Insights gained from imaging studies had led to the conclusion that the formation of the central adhesion domain in the IS is driven by active (ATP-driven) mechanisms. Recent studies, however, suggested that passive (thermodynamic) mechanisms may also play an important role in this process. Here, we present a simple physical model, taking into account the membrane-mediated thermodynamic attraction between the TCR-pMHC bonds and the effective forces that they experience due to ATP-driven actin retrograde flow and transport by dynein motor proteins. Monte Carlo simulations of the model exhibit a good spatio-temporal agreement with the experimentally observed pattern evolution of the TCR-pMHC microclusters. The agreement is lost when one of the aggregation mechanisms is "muted", which helps to identify their respective roles in the process. We conclude that actin retrograde flow drives the centripetal motion of TCR-pMHC bonds, while the membrane-mediated interactions facilitate microcluster formation and growth. In the absence of dynein motors, the system evolves into a ring-shaped pattern, which highlights the role of dynein motors in the formation of the final concentric pattern. The interplay between the passive and active mechanisms regulates the rate of the accumulation process, which in the absence of one them proceeds either too quickly or slowly.
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Affiliation(s)
- Nadiv Dharan
- Department of Biomedical Engineering, Ben Gurion University of the Negev, Be'er Sheva 84105, Israel.
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13
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Deshpande SA, Pawar AB, Dighe A, Athale CA, Sengupta D. Role of spatial inhomogenity in GPCR dimerisation predicted by receptor association–diffusion models. Phys Biol 2017; 14:036002. [DOI: 10.1088/1478-3975/aa6b68] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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14
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Effect of probe diffusion on the SOFI imaging accuracy. Sci Rep 2017; 7:44665. [PMID: 28333166 PMCID: PMC5363082 DOI: 10.1038/srep44665] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 02/13/2017] [Indexed: 01/19/2023] Open
Abstract
Live-cell super-resolution fluorescence imaging is becoming commonplace for exploring biological systems, though sample dynamics can affect the imaging quality. In this work we evaluate the effect of probe diffusion on super-resolution optical fluctuation imaging (SOFI), using a theoretical model and numerical simulations based on the imaging of live cells labelled with photochromic fluorescent proteins. We find that, over a range of physiological conditions, fluorophore diffusion results in a change in the amplitude of the SOFI signal. The magnitude of this change is approximately proportional to the on-time ratio of the fluorophores. However, for photochromic fluorescent proteins this effect is unlikely to present a significant distortion in practical experiments in biological systems. Due to this lack of distortions, probe diffusion strongly enhances the SOFI imaging by avoiding spatial undersampling caused by the limited labeling density.
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15
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Vega-Cabrera LA, Pardo-López L. Membrane remodeling and organization: Elements common to prokaryotes and eukaryotes. IUBMB Life 2017; 69:55-62. [DOI: 10.1002/iub.1604] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 12/15/2016] [Indexed: 01/14/2023]
Affiliation(s)
- Luz A. Vega-Cabrera
- Instituto de Biotecnología, Universidad Nacional Autónoma de México; Apdo. Postal 510-3 Cuernavaca Morelos México
| | - Liliana Pardo-López
- Instituto de Biotecnología, Universidad Nacional Autónoma de México; Apdo. Postal 510-3 Cuernavaca Morelos México
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16
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Schmid F. Physical mechanisms of micro- and nanodomain formation in multicomponent lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:509-528. [PMID: 27823927 DOI: 10.1016/j.bbamem.2016.10.021] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 10/19/2016] [Accepted: 10/27/2016] [Indexed: 12/17/2022]
Abstract
This article summarizes a variety of physical mechanisms proposed in the literature, which can generate micro- and nanodomains in multicomponent lipid bilayers and biomembranes. It mainly focusses on lipid-driven mechanisms that do not involve direct protein-protein interactions. Specifically, it considers (i) equilibrium mechanisms based on lipid-lipid phase separation such as critical cluster formation close to critical points, and multiple domain formation in curved geometries, (ii) equilibrium mechanisms that stabilize two-dimensional microemulsions, such as the effect of linactants and the effect of curvature-composition coupling in bilayers and monolayers, and (iii) non-equilibrium mechanisms induced by the interaction of a biomembrane with the cellular environment, such as membrane recycling and the pinning effects of the cytoplasm. Theoretical predictions are discussed together with simulations and experiments. The presentation is guided by the theory of phase transitions and critical phenomena, and the appendix summarizes the mathematical background in a concise way within the framework of the Ginzburg-Landau theory. This article is part of a Special Issue entitled: Lipid order/lipid defects and lipid-control of protein activity edited by Dirk Schneider.
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Affiliation(s)
- Friederike Schmid
- Institute of Physics, Johannes Gutenberg University, 55099 Mainz, Germany
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17
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Shah AD, Inder KL, Shah AK, Cristino AS, McKie AB, Gabra H, Davis MJ, Hill MM. Integrative Analysis of Subcellular Quantitative Proteomics Studies Reveals Functional Cytoskeleton Membrane-Lipid Raft Interactions in Cancer. J Proteome Res 2016; 15:3451-3462. [PMID: 27384440 DOI: 10.1021/acs.jproteome.5b01035] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Lipid rafts are dynamic membrane microdomains that orchestrate molecular interactions and are implicated in cancer development. To understand the functions of lipid rafts in cancer, we performed an integrated analysis of quantitative lipid raft proteomics data sets modeling progression in breast cancer, melanoma, and renal cell carcinoma. This analysis revealed that cancer development is associated with increased membrane raft-cytoskeleton interactions, with ∼40% of elevated lipid raft proteins being cytoskeletal components. Previous studies suggest a potential functional role for the raft-cytoskeleton in the action of the putative tumor suppressors PTRF/Cavin-1 and Merlin. To extend the observation, we examined lipid raft proteome modulation by an unrelated tumor suppressor opioid binding protein cell-adhesion molecule (OPCML) in ovarian cancer SKOV3 cells. In agreement with the other model systems, quantitative proteomics revealed that 39% of OPCML-depleted lipid raft proteins are cytoskeletal components, with microfilaments and intermediate filaments specifically down-regulated. Furthermore, protein-protein interaction network and simulation analysis showed significantly higher interactions among cancer raft proteins compared with general human raft proteins. Collectively, these results suggest increased cytoskeleton-mediated stabilization of lipid raft domains with greater molecular interactions as a common, functional, and reversible feature of cancer cells.
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Affiliation(s)
- Anup D Shah
- The University of Queensland Diamantina Institute, The University of Queensland , Translational Research Institute, Brisbane, Queensland 4102, Australia
| | - Kerry L Inder
- The University of Queensland Diamantina Institute, The University of Queensland , Translational Research Institute, Brisbane, Queensland 4102, Australia
| | - Alok K Shah
- The University of Queensland Diamantina Institute, The University of Queensland , Translational Research Institute, Brisbane, Queensland 4102, Australia
| | - Alexandre S Cristino
- The University of Queensland Diamantina Institute, The University of Queensland , Translational Research Institute, Brisbane, Queensland 4102, Australia
| | - Arthur B McKie
- Ovarian Cancer Action Research Centre, Department of Surgery and Cancer, Imperial College London Hammersmith Campus , London W12 0NN, United Kingdom
| | - Hani Gabra
- Ovarian Cancer Action Research Centre, Department of Surgery and Cancer, Imperial College London Hammersmith Campus , London W12 0NN, United Kingdom
| | - Melissa J Davis
- Division of Bioinformatics, The Walter and Eliza Hall Institute of Medical Research , 1G Royal Parade, Parkville Victoria 3052, Australia
| | - Michelle M Hill
- The University of Queensland Diamantina Institute, The University of Queensland , Translational Research Institute, Brisbane, Queensland 4102, Australia
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18
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Fowler PW, Williamson JJ, Sansom MSP, Olmsted PD. Roles of Interleaflet Coupling and Hydrophobic Mismatch in Lipid Membrane Phase-Separation Kinetics. J Am Chem Soc 2016; 138:11633-42. [PMID: 27574865 PMCID: PMC5025830 DOI: 10.1021/jacs.6b04880] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
![]()
Characterizing
the nanoscale dynamic organization within lipid
bilayer
membranes is central
to our understanding of cell membranes at a molecular level. We investigate
phase separation and communication across leaflets in ternary lipid
bilayers, including saturated lipids with between 12 and 20 carbons
per tail. Coarse-grained molecular dynamics simulations reveal a novel
two-step kinetics due to hydrophobic mismatch, in which the initial
response of the apposed leaflets upon quenching is to increase local
asymmetry (antiregistration), followed by dominance of symmetry (registration)
as the bilayer equilibrates. Antiregistration can become thermodynamically
preferred if domain size is restricted below ∼20 nm, with implications
for the symmetry of rafts and nanoclusters in cell membranes, which
have similar reported sizes. We relate our findings to theory derived
from a semimicroscopic model in which the leaflets experience a “direct”
area-dependent coupling, and an “indirect” coupling
that arises from hydrophobic mismatch and is most important at domain
boundaries. Registered phases differ in composition from antiregistered
phases, consistent with a direct coupling between the leaflets. Increased
hydrophobic mismatch purifies the phases, suggesting that it contributes
to the molecule-level lipid immiscibility. Our results demonstrate
an interplay of competing interleaflet couplings that affect phase
compositions and kinetics, and lead to a length scale that
can influence lateral and transverse bilayer organization within cells.
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Affiliation(s)
- Philip W Fowler
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford, OX1 3QU, U.K
| | - John J Williamson
- Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University , 37th and O Streets, N.W., Washington, D.C. 20057, United States
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford, OX1 3QU, U.K
| | - Peter D Olmsted
- Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University , 37th and O Streets, N.W., Washington, D.C. 20057, United States
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19
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Lin CY, Huang JY, Lo LW. Exploring in vivo cholesterol-mediated interactions between activated EGF receptors in plasma membrane with single-molecule optical tracking. BMC BIOPHYSICS 2016; 9:6. [PMID: 27347397 PMCID: PMC4919887 DOI: 10.1186/s13628-016-0030-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 06/06/2016] [Indexed: 11/10/2022]
Abstract
Background The first step in many cellular signaling processes occurs at various types of receptors in the plasma membrane. Membrane cholesterol can alter these signaling pathways of living cells. However, the process in which the interaction of activated receptors is modulated by cholesterol remains unclear. Methods In this study, we measured single-molecule optical trajectories of epidermal growth factor receptors moving in the plasma membranes of two cancerous cell lines and one normal endothelial cell line. A stochastic model was developed and applied to identify critical information from single-molecule trajectories. Results We discovered that unliganded epidermal growth factor receptors may reside nearby cholesterol-riched regions of the plasma membrane and can move into these lipid domains when subjected to ligand binding. The amount of membrane cholesterol considerably affects the stability of correlated motion of activated epidermal growth factor receptors. Conclusions Our results provide single-molecule evidence of membrane cholesterol in regulating signaling receptors. Because the three cell lines used for this study are quite diverse, our results may be useful to shed light on the mechanism of cholesterol-mediated interaction between activated receptors in live cells.
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Affiliation(s)
- Chien Y Lin
- Department of Photonics, Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu, Taiwan
| | - Jung Y Huang
- The T.K.P. Research Center for Photonics, Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu, Taiwan
| | - Leu-Wei Lo
- Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, 35, Keyan Road, Zhunan, Taiwan
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20
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Reigada R, Mikhailov AS. Equilibrium microphase separation in the two-leaflet model of lipid membranes. Phys Rev E 2016; 93:010401. [PMID: 26871009 DOI: 10.1103/physreve.93.010401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Indexed: 06/05/2023]
Abstract
Because of the coupling between local lipid composition and the thickness of the membrane, microphase separation in two-component lipid membranes can take place; such effects may underlie the formation of equilibrium nanoscale rafts. Using a kinetic description, this phenomenon is analytically and numerically investigated. The phase diagram is constructed through the stability analysis for linearized kinetic equations, and conditions for microphase separation are discussed. Simulations of the full kinetic model reveal the development of equilibrium membrane nanostructures with various morphologies from the initial uniform state.
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Affiliation(s)
- Ramon Reigada
- Departament de Química Física i Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Avinguda Diagonal 647, 08028 Barcelona, Spain
| | - Alexander S Mikhailov
- Abteilung Physikalische Chemie, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
- Department of Mathematics and Life Sciences, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8530, Japan
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21
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Lin CY, Huang JY, Lo LW. Unraveling the impact of lipid domains on the dimerization processes of single-molecule EGFRs of live cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:886-93. [DOI: 10.1016/j.bbamem.2014.12.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 11/21/2014] [Accepted: 12/18/2014] [Indexed: 10/24/2022]
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22
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Alvarez-Guaita A, Vilà de Muga S, Owen DM, Williamson D, Magenau A, García-Melero A, Reverter M, Hoque M, Cairns R, Cornely R, Tebar F, Grewal T, Gaus K, Ayala-Sanmartín J, Enrich C, Rentero C. Evidence for annexin A6-dependent plasma membrane remodelling of lipid domains. Br J Pharmacol 2015; 172:1677-90. [PMID: 25409976 DOI: 10.1111/bph.13022] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Revised: 11/11/2014] [Accepted: 11/14/2014] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND AND PURPOSE Annexin A6 (AnxA6) is a calcium-dependent phospholipid-binding protein that can be recruited to the plasma membrane to function as a scaffolding protein to regulate signal complex formation, endo- and exocytic pathways as well as distribution of cellular cholesterol. Here, we have investigated how AnxA6 influences the membrane order. EXPERIMENTAL APPROACH We used Laurdan and di-4-ANEPPDHQ staining in (i) artificial membranes; (ii) live cells to investigate membrane packing and ordered lipid phases; and (iii) a super-resolution imaging (photoactivated localization microscopy, PALM) and Ripley's K second-order point pattern analysis approach to assess how AnxA6 regulates plasma membrane order domains and protein clustering. KEY RESULTS In artificial membranes, purified AnxA6 induced a global increase in membrane order. However, confocal microscopy using di-4-ANEPPDHQ in live cells showed that cells expressing AnxA6, which reduces plasma membrane cholesterol levels and modifies the actin cytoskeleton meshwork, displayed a decrease in membrane order (∼15 and 30% in A431 and MEF cells respectively). PALM data from Lck10 and Src15 membrane raft/non-raft markers revealed that AnxA6 expression induced clustering of both raft and non-raft markers. Altered clustering of Lck10 and Src15 in cells expressing AnxA6 was also observed after cholesterol extraction with methyl-β-cyclodextrin or actin cytoskeleton disruption with latrunculin B. CONCLUSIONS AND IMPLICATIONS AnxA6-induced plasma membrane remodelling indicated that elevated AnxA6 expression decreased membrane order through the regulation of cellular cholesterol homeostasis and the actin cytoskeleton. This study provides the first evidence from live cells that support current models of annexins as membrane organizers.
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Affiliation(s)
- Anna Alvarez-Guaita
- Departament de Biologia Cel·lular, Immunologia i Neurociències, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain
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23
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Lin CY, Huang JY, Lo LW. Energetic modeling and single-molecule verification of dynamic regulation on receptor complexes by actin corrals and lipid raft domains. J Chem Phys 2014; 141:215102. [DOI: 10.1063/1.4902985] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Chien Y. Lin
- Department of Photonics, Chiao Tung University, Hsinchu 300, Taiwan
| | - Jung Y. Huang
- The T.K.B. Research Center of Photonics, Chiao Tung University, Hsinchu 300, Taiwan
| | - Leu-Wei Lo
- Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, Zhunan, Miaoli 350, Taiwan
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24
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Sadeghi S, Vink RLC. Membrane sorting via the extracellular matrix. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:527-31. [PMID: 25450353 DOI: 10.1016/j.bbamem.2014.10.035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 10/06/2014] [Accepted: 10/21/2014] [Indexed: 12/16/2022]
Abstract
We consider the coupling between a membrane and the extracellular matrix. Computer simulations demonstrate that the latter coupling is able to sort lipids. It is assumed that membranes are elastic manifolds, and that this manifold is disrupted by the extracellular matrix. For a solid-supported membrane with an actin network on top, regions of positive curvature are induced below the actin fibers. A similar mechanism is conceivable by assuming that the proteins which connect the cytoskeleton to the membrane induce local membrane curvature. The regions of non-zero curvature exist irrespective of any phase transition the lipids themselves may undergo. For lipids that prefer certain curvature, the extracellular matrix thus provides a spatial template for the resulting lateral domain structure of the membrane.
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Affiliation(s)
- Sina Sadeghi
- Institute of Theoretical Physics, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany.
| | - Richard L C Vink
- Institute of Theoretical Physics, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
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25
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Manyuhina OV. Protein crowding on biomembranes: analysis of contour instabilities. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:022713. [PMID: 25215764 DOI: 10.1103/physreve.90.022713] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Indexed: 06/03/2023]
Abstract
Collective behavior of proteins on biomembranes is usually studied within the spontaneous curvature model. Here we consider an alternative phenomenological approach, which accounts consistently for partial ordering of proteins as well as the anchoring forces exerted on a membrane by layer of proteins. We show analytically that such anisotropic interactions can drive membrane bending, resulting in nontrivial equilibrium morphologies. The predicted instabilities can advance our conceptual understanding of physical mechanisms behind collective phenomena in biological systems, in particular those with inherent anisotropy.
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Affiliation(s)
- O V Manyuhina
- Nordita, Royal Institute of Technology, and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden and Physics Department, Syracuse University, Syracuse, New York 13244, USA
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26
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Strahl H, Bürmann F, Hamoen LW. The actin homologue MreB organizes the bacterial cell membrane. Nat Commun 2014; 5:3442. [PMID: 24603761 PMCID: PMC3955808 DOI: 10.1038/ncomms4442] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 02/13/2014] [Indexed: 02/07/2023] Open
Abstract
The eukaryotic cortical actin cytoskeleton creates specific lipid domains, including lipid rafts, which determine the distribution of many membrane proteins. Here we show that the bacterial actin homologue MreB displays a comparable activity. MreB forms membrane-associated filaments that coordinate bacterial cell wall synthesis. We noticed that the MreB cytoskeleton influences fluorescent staining of the cytoplasmic membrane. Detailed analyses combining an array of mutants, using specific lipid staining techniques and spectroscopic methods, revealed that MreB filaments create specific membrane regions with increased fluidity (RIFs). Interference with these fluid lipid domains (RIFs) perturbs overall lipid homeostasis and affects membrane protein localization. The influence of MreB on membrane organization and fluidity may explain why the active movement of MreB stimulates membrane protein diffusion. These novel MreB activities add additional complexity to bacterial cell membrane organization and have implications for many membrane-associated processes. The formation of lipid domains in eukaryotic cells is controlled by the cortical actin cytoskeleton. Here, the authors show that the bacterial actin homologue MreB has a comparable activity, influencing the formation of regions of increased fluidity that determine the distribution of membrane proteins.
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Affiliation(s)
- Henrik Strahl
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle NE2 4AX, UK
| | - Frank Bürmann
- Max Planck Institute of Biochemistry, Chromosome Organization and Dynamics, Am Klopferspitz 18, Martinsried D-82152, Germany
| | - Leendert W Hamoen
- 1] Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle NE2 4AX, UK [2] Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Amsterdam 1098 XH, The Netherlands
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